SOME ECOLOGICAL ASPECTS OF AQUATIC CYTOPHAGAS

Abstract

Cytophaga-like bacteria are at least temporarily abundant in almost all aquatic habitats, although the techniques which are currently available for large scale identification and enumeration, may only lead to rather vague taxonomic conclusions. As for obtaining maximal plate counts, the enumeration of relatively fastidious and mostly organic nitrogen-requiring marine forms could be considerably improved by using 38 mg/l of polymyxin B as a counterselective agent. From a collection of chitin-degrading and predominantly estuarine bacteria, Cytophagaceae= strains were selected to study utilization of glucose ‚production of depolymerizing enzymes and survival under hydrostatic pressure. While swarming (spreading) as one of the most striking colony features was insufficient as taxonomic indicator, Cytophaga-like isolates could be classified on the basis of their substrate requirements for swarming. Different swarming types could at least partly be ranked according to their kinetic parametere for glucose utilization. While being able to degrade various biopolymers effectively even at low water temperatures, psychrotrophic, oligonitrophilic isolates suggest a key position for this type of freshwater cytophagas in major biogeochemical pathways of the carbon cycle. Growth rates,production of chitin-degrading enzymes as well as autolytic activities of one of these isolates (Cytophaga johnsonae, strain C 21) were characterized by similar temperature responses. In contrast to deep freshwater habitats, nothing is known about a corresponding contribution of marine Cytophaga spp. to biodegradation processes in the deep sea. It could be shown,however, that even a starved culture of an estuarine surface water isolate was able to survive hydrostatic pressures up to 500 at .